feat: add Go backend compatibility service scaffold

go-backend/internal/auth/jwt.go

@@ -0,0 +1,121 @@
+package auth
+
+import (
+	"crypto/hmac"
+	"crypto/sha256"
+	"encoding/base64"
+	"encoding/json"
+	"errors"
+	"strconv"
+	"time"
+)
+
+const (
+	algorithm  = "HmacSHA256"
+	expireTime = 90 * 24 * time.Hour
+)
+
+type Claims struct {
+	Sub    string `json:"sub"`
+	Iat    int64  `json:"iat"`
+	Exp    int64  `json:"exp"`
+	User   string `json:"user"`
+	Name   string `json:"name"`
+	RoleID int    `json:"role_id"`
+}
+
+type tokenHeader struct {
+	Alg string `json:"alg"`
+	Typ string `json:"typ"`
+}
+
+func GenerateToken(userID int64, username string, roleID int, secret string) (string, error) {
+	now := time.Now()
+	header := tokenHeader{Alg: algorithm, Typ: "JWT"}
+	claims := Claims{
+		Sub:    strconv.FormatInt(userID, 10),
+		Iat:    now.Unix(),
+		Exp:    now.Add(expireTime).Unix(),
+		User:   username,
+		Name:   username,
+		RoleID: roleID,
+	}
+
+	headerPart, err := encodeJSON(header)
+	if err != nil {
+		return "", err
+	}
+	payloadPart, err := encodeJSON(claims)
+	if err != nil {
+		return "", err
+	}
+	sig := sign(headerPart+"."+payloadPart, secret)
+
+	return headerPart + "." + payloadPart + "." + sig, nil
+}
+
+func ValidateToken(token, secret string) (Claims, bool) {
+	claims, err := ParseClaims(token, secret)
+	if err != nil {
+		return Claims{}, false
+	}
+	return claims, true
+}
+
+func ParseClaims(token, secret string) (Claims, error) {
+	parts := splitToken(token)
+	if len(parts) != 3 {
+		return Claims{}, errors.New("invalid token")
+	}
+
+	signedContent := parts[0] + "." + parts[1]
+	expected := sign(signedContent, secret)
+	if !hmac.Equal([]byte(expected), []byte(parts[2])) {
+		return Claims{}, errors.New("invalid signature")
+	}
+
+	payloadBytes, err := base64.RawURLEncoding.DecodeString(parts[1])
+	if err != nil {
+		return Claims{}, err
+	}
+
+	var claims Claims
+	if err := json.Unmarshal(payloadBytes, &claims); err != nil {
+		return Claims{}, err
+	}
+
+	if claims.Exp <= time.Now().Unix() {
+		return Claims{}, errors.New("token expired")
+	}
+
+	return claims, nil
+}
+
+func splitToken(token string) []string {
+	parts := make([]string, 0, 3)
+	current := ""
+	for i := 0; i < len(token); i++ {
+		if token[i] == '.' {
+			parts = append(parts, current)
+			current = ""
+			continue
+		}
+		current += string(token[i])
+	}
+	parts = append(parts, current)
+	return parts
+}
+
+func encodeJSON(v interface{}) (string, error) {
+	raw, err := json.Marshal(v)
+	if err != nil {
+		return "", err
+	}
+	return base64.RawURLEncoding.EncodeToString(raw), nil
+}
+
+func sign(content, secret string) string {
+	h := hmac.New(sha256.New, []byte(secret))
+	h.Write([]byte(content))
+	return base64.RawURLEncoding.EncodeToString(h.Sum(nil))
+}